Vitamin D

Cholecalciferol (D3), ergocalciferol (D2), calcifediol

Fat-soluble vitamins

Aliases / common names

D3; D2; sunshine vitamin; 25-hydroxyvitamin D (blood marker)

Natural food sources

Sunlight-driven skin synthesis; fatty fish, cod liver oil, egg yolk, fortified milk and cereals.

Main wellness functions

Supports calcium absorption, bone and teeth mineralization, muscle and immune function.

Deficiency signs

Rickets in children, osteomalacia in adults, bone pain, muscle weakness and higher fall risk.

Recommended intake

Adults and children >1 year: 15 mcg/day (600 IU). Adults >70: 20 mcg/day (800 IU). Pregnancy: 15 mcg/day. Adult UL: 100 mcg/day (4,000 IU).

Excess intake effects

Excess can cause hypercalcemia, nausea, vomiting, kidney stones, kidney injury and arrhythmia.

Contraindicated / caution groups

Use caution with hypercalcemia, sarcoidosis, severe kidney disease, kidney stones, thiazide diuretics or digoxin.

Common dosage forms

Softgels, drops, tablets, sprays; D3 is most common, D2 is vegan-suitable in some products.

Common product strengths

10-50 mcg (400-2,000 IU) daily; 125 mcg (5,000 IU) high-strength products; combined with K2 or calcium.

Use precautions

For long-term high-dose use, monitor serum 25(OH)D and calcium. Take with meals containing fat.

Supplement notes

Requirements vary with sun exposure, skin tone, age, latitude and clothing habits.

This information is for general nutrition education and product reference only. It does not replace medical diagnosis, treatment or individualized dietary advice.